Sorry, but totally wrong. Poodles DO make the pool more dense. Obvious if you think about it. Weigh the water without poodles. Weigh it with poodles in it. Compensate for the difference in volume. The density is higher.
Imagine putting a condensed neutron star the size of a fist into a pool and then weighing the contents of the pool. Denser as a sample, even if not uniform.
Would putting a poodle in a bathtub affect a hydrometer a foot away? No. But put a million poodles in a tub the size of a ship,let them sink, and use a giant hydrometer (lighter than poodles) that rested among them, and the density difference would show. It would sit on top of a layer of poodles.
This is not about huge particles like poodles. It's about tiny,slick particles than blend in with the fluid. And unlike poodles, proteins and yeast globs and so on don't go all the way to the bottom.
This is hard to explain to people who don't have physics backgrounds, but it's not a binary thing.
Think of a can of tomato juice that hasn't been shaken. The solids do not go to the bottom. They form a thick layer next to the bottom, just like the solids in my beer. If you were to measure the gravity of that layer, you would find it higher than the density of the clear liquid above it. There is more mass in it per unit of volume.
The hydrometer bulb rests in a deep layer of liquid full of heavy solids that have fallen lower in the column, so it measures the density of that layer.
This reminds me of a funny story one of my profs told me when I was in grad school in physics. He told it to show how people who think they know more than they do have to be careful. His name was Larry Shepley. He came out of Princeton's Institute for Advanced Studies. Larry said he had seen this question asked in a room full of top physicists, and every single one got it wrong.
Anyway, he said you take unhomogenized milk and shake it. Then you put it down. How do you measure the pressure at a given point? Knowing he asked so I could say something wrong, I said what the other guys said. I didn't try to figure it out. I said you measure the depth at that point. He said, "That is, of course, wrong."
Because the milk isn't homogeneous, the density varies with the depth, so it's not linear. You don't know how much mass is above the point of measurement. You have to know that in order to know the pressure.
Pressure is what drives a hydrometer. Pascal's principle. The molecules in the fluid push in every direction, including up.
My beer is like the settling milk. You have to measure it right away, not after the cream begins to rise.
There were no bubbles. Evaporation over hours didn't matter. Everything was clean. I compensated for temperature every time. It's the solids.
Topic: SG Going Up and Down (Read 914 times)
